The present invention relates to a device for separating impurities from the lubricating oil of an internal combustion engine, said device comprising a filter element, wherein said filter element is arranged in a two-piece housing that is closed during operation of the device and comprises a stationary lower housing part and a removable upper screw cap and wherein said screw cap and said filter element comprise detachable connection means which can be brought into contact and are used to transmit axial tractive forces, wherein the filter element is removed from the housing by means of these connection means when the screw cap is rotated in its loosening rotational direction.
Furthermore, the present invention relates to a device for separating impurities from the lubricating oil of an internal combustion engine, said device comprising a filter element at its bottom and, on top of said filter element, a centrifuge with a rotor drivable by means of lubricating oil flowing through it, wherein said filter element and said centrifuge are arranged, one above the other, in a common two-piece housing that is closed during operation of the device and comprises a removable upper screw cap and a stationary lower housing part, wherein a removable intermediate cap is arranged in the housing between said filter element and said centrifuge, said intermediate cap and said filter element comprising first detachable connection means which can be brought into contact and are used to transmit axial tractive forces, and wherein said centrifuge, said intermediate cap and said filter element can be removed from the housing while the latter is in its open state.
A device of the first aforementioned type is, for example, known from DE 296 10 290 U1, which describes a device that is designed as a fluid filter and which provides that the upper end disk of the filter element is provided with locking tongues that are projecting towards the top and can be mounted elastically. With the device being in the assembled state, these locking tongues engage a continuous locking groove extending along the internal perimeter of the screw cap. This permits removal of the screw cap, along with the filter element, from the filter housing by rotating said screw cap in its loosening rotational direction, this allowing the filter element to be handled easily when being replaced, wherein it is not necessary to directly seize the dirty and oily filter element. Usually, a used-up filter element is separated from the screw cap by canting the two parts against each other until the locking connection is undone. This requires canting beyond a certain angle to ensure that the locking connection will indeed be undone. In the case of screw caps which provide only little lateral motional play for the filter element partially arranged therein, this especially being the case with relatively long screw caps, it is not possible to undo the locking connection by canting because the deflection angle required between the two parts fails to be achieved since the filter element touches the internal perimeter of the screw cap beforehand. In this case, great effort is required to undo the locking connection by exerting a tractive force in an axial direction. To achieve this, the dirty filter element must be seized, and in this process, contaminated lubricating oil may easily be released into the environment. In addition, it is difficult to exert the necessary tractive force at all when seizing an oily filter element.
A device of the second aforementioned type is known from DE 43 06 431 C1. If the screw cap, as a removable part of the housing of this known device, is rotated in its loosening rotational direction, initially only the screw cap, in its thread, moves away from the stationary part of the housing in an upward direction, whereas the centrifuge rotor that is arranged in the upper part of the housing remains in its position. After the housing cap has been removed, the rotor of the centrifuge is positioned in its lower bearing. In the next step, the centrifuge rotor can be removed. Thereafter, the intermediate cap is accessible. The intermediate cap must be pulled out of the lower part of the housing in an upward direction. Therein, the intermediate cap takes along the filter element that is arranged below it, thus also removing it in an upward direction. This taking along is initiated by the first detachable connection means between the intermediate cap and the upper end disk of the filter element. After the combined unit consisting of intermediate cap and filter element has been removed, the filter element can, by canting or by exerting a tractive force in axial direction, be disengaged from and pulled out of the intermediate cap, and a new filter element can be inserted in the intermediate cap and engaged therewith via the detachable connection means by exerting a thrust force in axial direction. As compared with its disassembly, the device is then assembled in reverse order by first introducing the intermediate cap including filter element in the lower part of the housing. Thereafter, the centrifuge rotor is placed onto the intermediate cap with its lower bearing. Finally, the screw cap is screwed on, while it must be ensured that the upper bearing of the centrifuge rotor assumes its desired position in the center of the upper end of the screw cap. Obviously, disassembly and assembly of this device are relatively complicated and troublesome. In addition, disassembly requires that oily parts, in particular the intermediate cap, be seized manually. Apart from operating personnel getting their hands dirty, this poses the further problem that it is difficult to get a sufficiently firm hold of the intermediate cap because of its oily surface. As a result, it is even more difficult to pull out the intermediate cap from the lower part of the housing against the developing frictional forces and against a vacuum that might possibly be present.